In recent years, in mobile communication, various kinds of information such as images and data other than speech have become targets of transmission. In association with this, the need for highly reliable and high-speed transmission has further increased. However, when high-speed transmission is carried out in mobile communication, the influence of delayed waves due to multipath cannot be ignored, and transmission characteristics deteriorate due to frequency selective fading.
Multicarrier communication typified by an OFDM (Orthogonal Frequency Division Multiplexing) scheme is attracting attention as one of techniques for combating frequency selective fading. Multicarrier communication is a technique for performing high-speed transmission by transmitting data using a plurality of subcarriers whose transmission rate is suppressed to the degree where frequency selective phasing does not occur. Particularly, in the OFDM scheme, the frequencies of a plurality of subcarriers where data are arranged are orthogonal each other, and therefore this scheme provides highest spectrum efficiency use in multicarrier communication and can be implemented using a relatively simple hardware configuration. Therefore, the OFDM scheme attracts attention as a candidate for a communication scheme adopted in the fourth generation mobile communication, and various studies have been undertaken.
Further, in the OFDM scheme, as an additional reception error countermeasure, there is a technique of duplicating (repeating) the same data symbol to obtain a plurality of symbols, mapping these symbols in a plurality of subcarriers, that is, arranging a plurality of the same data in the frequency domain and then performing transmission (see, for example, Non-patent Document 1). In an OFDM communication apparatus that adopts this technique, when the number of repetitions (the number of duplicates) is RF (Repetition Factor), each of the transmission symbols is copied in the number of RFs, and the symbols are arranged on the frequency domain and transmitted. This RF may be defined as a parameter corresponding to a spreading factor of the CDMA scheme. Non-patent Document 1: Maeda, Atarashi, Kishiyama, Sawahashi, “Performance Comparisons between OFCDM and OFDM in a Forward Link Broadband Channel,” Technical Report RCS2002-162 of IEICE, August 2002